How obesity makes it harder to taste

Inflammation linked to the disease caused the loss of taste buds in mice

BYE BYE BUDS Mice that became obese on a high-fat diet (right) lost a quarter of their taste buds (stained red) and also had fewer progenitor cells (stained green) — which give rise to new taste buds — than mice of a healthy weight on a regular diet (left).

As mice plumped up on a high-fat diet, some of their taste buds vanished. This disappearing act could explain why some people with obesity seem to have a weakened sense of taste, which may compel them to eat more.

Compared with siblings that were fed normal mouse chow, mice given high-fat meals lost about 25 percent of their taste buds over eight weeks. Buds went missing because mature taste bud cells died off more quickly, and fewer new cells developed to take their place. Chronic, low-level inflammation associated with obesity appears to be behind the loss, researchers report March 20 in PLOS Biology.

Taste buds, each a collection of 50 to 100 cells, sense whether a food is sweet, sour, bitter, salty or umami (savory). These cells help identify safe and nourishing food, and stimulate reward centers in the brain. The tongue’s taste bud population is renewed regularly; each bud lasts about 10 days. Special cells called progenitor cells give rise to new taste bud cells that replace old ones.

Some studies have suggested that taste becomes duller in people with obesity, although why that is has remained unclear. But if taste becomes less intense, “then maybe you don’t get the positive feeling that you should,” which could give way to more overeating, says study coauthor Robin Dando, who studies the biology of taste at Cornell University. Nearly 40 percent of U.S. adults have obesity, determined by a person’s body mass index, a ratio of weight to height. The condition is linked to a number of health problems, including heart disease, diabetes and cancer.

The study’s finding that obesity-induced inflammation impacts the presence of taste buds “provides a possible link between obesity and taste,” says Kathryn Medler, a taste physiologist at the University at Buffalo in New York, who was not involved with the research.

Obesity triggers low-level, ongoing inflammation in the body, which can harm cells. The taste tissues of the obese mice had a higher amount of a type of protein called a cytokine, which regulates inflammation, than their normal-weight kin, the researchers found.

This particular cytokine, called tumor necrosis factor alpha, seems to be damaging to taste buds, the researchers found. In a test with mice that couldn’t make the cytokine, the obese mice didn’t have missing taste buds. Another experiment showed that mice engineered not to gain excess weight on the high-fat diet — and that therefore didn’t have obesity-related inflammation — also had the regular amount of taste buds.

Along with learning more about how taste buds are damaged by inflammation, Dando is interested in working toward new treatments for obesity, perhaps by countering the dulled sense of taste. “These mice lose taste buds,” he says. “Can we bring them back?”